The invention relates to a stepless hydrostatic mechanical transmission with power distribution splitting to be used between a prime mover and a power output train comprising:
an epicyclic differential made up of at least four shafts, two sun wheels, at least two plant wheels meshing respectively with said sun wheels, a web bearing the said plant wheels and an annulus, PA1 two main shafts constituting an input and an output respectively and connected with respectively different ones of the shafts of the epicyclic differential, PA1 and at least two hydrostatic machines, which respectively in at least one working range of the said power distribution transmission are adapted to be connected with their own shafts of the epicyclic differential and are adapted to be operated as pumps and motors
at least one of said hydrostatic machines being adapted to be changed over by a clutch, when the other respective hydrostatic machine is stationary and on transition from one such working range to another, from the main shaft on the output side to the sun wheel not on the drive side and, during traction operation, from the motor function to the pump function.
The invention takes as a starting point the device as described in the German patent 2,904,572 and its US equivalent U.S. Pat. No. 4,313,351 in the form of a stepless hydrostatic mechanical power transmission adapted to be used as part of a drive system, as for instance part of the drive system of a vehicle, whose epicyclic differential is so designed that the small sun wheel thereof is placed between a large sun wheel and a drive motor. As a result of this the shaft carrying the small sun wheel and not arranged on the drive side, had to be in the form of a hollow shaft and arranged to coaxially surrounding the input shaft bearing the large sun wheel. Since the size of such epicyclic differentials is dependent on there being a small sun wheel, such a design and configuration of the two sun wheels and their shafts also dictated the overall size of the power transmission. Therefore, dependent on the power requirement practical design problems arose as regards the accommodation of the prime mover, for instance in a vehicle, more especially if a power storing flywheel was provided as part of a brake energy recovery system.